Jet combustion fuel



UNITED STATES PATENT OFFICE JET COMBUSTION FUEL Jack M. Godsey, Wenonah, N. J assignor to Socony-Vacuum Oil Company, Incorporated, a corporation of New York No Drawing. Application May 24, 1949, Serial No. 95,151

9 Claims. 1

This invention is directed to improved fuels utilizable in jet combustion devices. It is particularly directed to jet combustion fuels having improved jet combustion properties through the Benzol, an excellent fuel, has a rate of flame propagation of about 1.6 feet per second, at a fuel mixture temperature of 230 F., a pressure of 1 atmosphere, and an air flow rate of' 3.15

addition thereto of small amounts of an additive 5 pounds/hour. material. As is well known to those familiar with the The simplest form of jet combustion mechaart, in the operation of jet combustion devices, nism is a tube with one end closed, in which a deposits of a sootlike character are formed within combustible is burned. The expanding gases of the combustion chamber and in subsequent porcombustion issuing from the open end of the tube tions of the apparatus. These deposits cause give rise to a reaction effect which drives the tube operating difficulties by interfering with comin a direction opposite to that of the emission of bustion in the combustion chamber and by the gases. The most complicated forms presently damaging the turbine. proposed consist of the same propulsion or jet The present invention is predicated upon the tube, plus a compressor to supply air for comdiscovery that small amounts of thiophene tar, bustion, plus a gas turbine which extracts enough disclosed in U. S. Patent No. 2,450,659, or of exenergy from the departing gases to drive the tracts of thiophene tar obtained by solvent treatcompressor. In present commercial forms, the merit, when added to a fuel, will materially imcompressor and turbine are assembled axially prove the combustion stability thereof. upon a common shaft, spaced far enough apart Further, it has been found that small amounts to permit a number of combustion chambers to of thiophene tar or of extracts of thiophene tar be arranged about the shaft between the comobtained as hereinafter disclosed, when mixed pressor and turbine with an exhaust tube extendwith fuels used in jet combustion devices, maing rearwardly from the turbine. In essence, the terially reduce the soot deposits formed during term jet combustion, as now commonly applied, combustion. and as used in this specification, refers to a As shown in U. S. Patent No. 2,450,659 and in method of combustion wherein fuel is continucopending application for Letters Patent, Serial ously introduced into and continuously burned in Number 721,453, filed on January 10, 1947, now a confined space for the purpose of deriving power U. S. Patent No. 2,515,927, issued on July 18, 1950, directly from the hot products of combustion. thiophene tar and thiophene are prepared by In practice, the range of conditions over which separately preheating sulfur and one or more a jet combustion device may operate may become normal aliphatic hydrocarbons selected from the quite limited for ill-chosen or ill-adapted fuels. group consisting of normal butane, normal Even though a combustible mixture be present, butenes, and butadienes, to temperatures such the flame will be blown out if the rate of fuel feed that combining sulfur and the hydrocarbon mais too far increased. Yet, high rates of fuel feed terial will give a mixture having a temperature are necessary to obtain high heat release, which in excess of about 450 0., mixing the preheated is high power delivery. Fuels with low blow-out sulfur and the preheated hydrocarbon mixture, levels can furnish only limited power and limited maintaining the temperature of the mixture at a flexibiilty under conditions of operation. Consetemperature in excess of about 450 C. for a period quently, the flame stability of a fuel is of major of time of at least 0.01 second and reducing the importance. temperature of the mixture to less than 450 C. It has been found that flam stability of a fuel Along with thiophene tar and thiophene, hydrois correlated with a property of the fuel which gen sulfide and small amounts of carbon disulflde is readily reproducible on a laboratory basis, using are also formed in the process. apparatus which is simple when compared to a It has been found in the operation of this commercial combustion tube, and with considerprocess that the relative proportions of sulfur ably less procedural difficulty. This correlated and hydrocarbon material in the charge may be property is the rate of flame propagation as varied over wide limits. Too much sulfur, howmeasured in a Bunsen-type burner, using the ever, results in poor efficiency in sulfur utilizamethod of Smith and Pickering [J. Res. Natl. ti n p r pa s a f v the c l t sulfuriza- Bur. Stds. 17, (1936)]. In this procedure, the tion of hydrocarbon material to carbon disulfide. rate of flame propagation is measured at a num. Yet, too low a proportion of sulfur lowers the her of fuel-air ratios by photographing the flame Conversion per pass and ultimate yiel by and measuring the slope of the flame cone. Decreasing the overall thermal degradation of hysirable levels of commercial operability may be found in fuels having rates of flame propagation of the order of 1.4 feet per second and higher.

drocarbon material. Generally speaking, best results are obtained using a weight ratio of sulfur to a hydrocarbon material varying between about 3 0.5 and about 4.0, although when butenes and butadienes constitute the bulk of the hydrocarbon charge, the lower limit of the weight ratio may be lower than 0.5. It should be observed, however, that for economical operation of the process, it is preferred not to use a hydrocarbon charge consisting predominantly of butadienes because of their tendency to polymerize under the condia found in this connection, that the reaction temperature may vary between about 450 C. and about 760 C. and, preferably, between about 540 C. and about 650 C. when butane is the predominant hydrocarbon reactant in the charge, and between about 480 C. and about 590 0. when butenes and butadienes are the predominant hydrocarbon reactants in the charge. Below the lower limit of the temperature range (about 450 C.), the reaction is so slow as to require a large throughput of sulfur and a higher ratio of hydrocarbon recycle for a fixed amount of end product, thereby detracting from the economics of the operation. Above the upper limit of the temperature range, the secondary reaction of degradation of hydrocarbon material in the charge takes precedence, thereby decreasing the yield of desired product. In addition to this, high temperatures favor the formation of carbon disulfide. It must be noted, also, that at these high temperatures corrosion problems are at a maximum, corrosion increasing perceptibly with increasing temperature.

It has also been found, in connection with this process, that the optimum reaction time depends upon the temperature employed. In general, other variables remaining constant, the lower the temperature, the longer the reaction time. The reaction or contact time and the reaction temperature are somewhat fixed, one in relation to the other, by the degree of degradation of the hydrocarbon material in the charge and by the effect of formation of undesirable products which may be tolerated. Thus, too long a contact time at high temperature results in severe cracking of the hydrocarbon material in the charge. The reaction proceeds with extreme speed, the only apparent limitation being the rapidity with which heat can .be supplied to the reaction mixture. The reaction is highly endothermic, requiring by experimental measure approximately 28,000 calories per gram molecular weight of thiophene produced from normal butane. The lower limit of the range of reaction time is fixed, therefore, by the engineering problem of heat transfer and by mechanical limitations such as allowable pressure drop across the reactor. Relatively long reaction times at temperatures in the neighborhood of the lower limit of the temperature range result in insuflicient reaction. Accordingly, it has been found that for best results the time of reaction is fixed by the reaction temperature.

In view of the foregoing, the criteria to be used in determining optimum operating temperatures within the range of 450 C. to 760 C. depend on the degree of conversion desired commensurate with operating costs, such as heat input and equipment cost, bearing in mind that within limits, the shorter the reaction time, and accordingly the higher the temperature, the larger the amount of end product which can be realized from a unit of given size per day.

While the relationship between the temperature of reaction and reaction time is not peculiar to the present process, it has been found that thiophene tar and thiophene may be produced by reacting sulfur and the aforesaid 4-02.1b0n hydrocarbons at a temperature between about 450 C. and about 760 C. for a period of time selected to minimize the yields of secondary reaction products such as carbon disulfide, cokelike materials and the like at the selected temperature. Under such conditions, when operating continuously with a reactor coil of suitable size and at a practical charge rate, it has been found that the lowest practical limit of the time of reaction is of the order of 0.01 second at about 760 C. The upper practical limit of the reaction time, other variables remaining constant, will correspond to the lower limit of the reaction temperature and may be of the order of several seconds.

Separate preheating of the hydrocarbon reactant and sulfur and quenching of the reaction mixture are necessary for achieving the somewhat close control of the reaction time at a given reaction temperature. This is very important in producing the specific reaction products, thiophene and thiophene tar. It is suspected that a number of reactions occur upon contacting the hydrocarbon reactant with sulfur. In this connection, the following should be noted: cracking of the hydrocarbon reactant destroying the l-carbon atom chain structure (said -carbon atom chain structure being a prerequisite for the formation of thiophene), formation of thiophene tars high in sulfur and formation of carbon disulflde. Ihese reactions compete with one another. It has been found that the rates of the formation of lighter hydrocarbons and of the formation of carbon disulfide are somewhat slower than those required for the formation of thiophene and thiophene tar. Accordingly, proper control of the reaction time at a given reaction temperature, achieved by separate preheating, mixing, heating at a given temperature for a corresponding period of time, and quenching is necessary to produce high yields of thiophene and thiophene tar with limited yields of carbon disulfide, coke-like materials, and fixed gases, due to limited decomposition of the hydrocarbon product. The rate of the reaction producing thiophene tar is fairly close to that required for the formation of thiophene, and the yields of thiophene tar and of thiophene are approximately the same. Upon standing, the thiophene tar separates from the other products and a separation can be made by decantation or other suitable separating means.

In this process the reaction is effected preferably at atmospheric pressure or under sufiicient pressure to cause the flow of the reactants through the reactor and auxiliary system under the desired reaction conditions. Tests have shown that the conversion per pass and ultimate yield of thiophene decreases with increasing pressure. However, even at appreciable pressures, thiophene and thiophene tar are, nevertheless, produced in substantial amounts.

The following example will serve as an illustration:

Example A mixture containing 30 per cent by volume of 1,3-butadiene and '70 per cent by volume of normal butane was charged into a preheater at a rate of 35 grams per minute and heated to a temperature of 590 C. Sulfur was charged to a separate preheater at a rate of 28 grams per minute and heated to a temperature of 590 C. The two streams were sent through a mixing nozzle and then through a baflied tube reactor constructed of 27 per cent chromium stainless steel, maintained at a temperature of 650 C. The reaction product was quenched with a water spray passed through a small Cottrell precipitator to remove tar mist and scrubbed through a hot countercurrent caustic tower. Liquid product was condensed and separated in a water cooler and ice trap and the residual gas was metered.

used falls within the range varying between.

about 0.1 per cent and 2.0 per cent by weight. The thiophene tar has limited solubility in certain base fuels, being less than 2.0 per cent in some cases. Its solubility will, of course, differ in fuels of different characteristics. The extracts of thiophene tar, on the other hand, being completely soluble in all jet combustion fuels, do not present this difficulty thereby permitting the use of a larger percentage of additive mate-- rial than may be possible with the thiophene tar. The extracts of thiophene tar are usually added to the base fuel in amounts between about 0.1 per cent and about 2.0 per cent by weight. Greater amounts, up to per cent, may be used if desired, although, in general, no outstanding results seem to occur. Conceivably and within the scope of the present invention, these additives may be added to jet fuels to be marketed or procured as concentrates, viz., jet combustion" fuels containing upwards of 10 per cent and up to 49 per cent by weight of the additive. These concentrates are subsequently added to a jet combustion fuel in such proportions as to produce the effective concentration of additive in the fuel desired, i. e., a sufficient amount to improve the jet combustion properties of the jet combustion fuel.

The thiophene tar extracts are obtained by treating the thiophene tar with a C3-C1o alkane hydrocarbon or mixtures of C3-C1o alkane hydrocarbons. Typical of these C3-C1o alkane hydrocarbons, are propane, isobutane, 1,3-dimethyl pentane, n-hexane, 2,3-ethyl-methyl hexane, and n-decane. alkane hydrocarbons. In the preparation of these extracts, the thiophene tar is contacted with the hydrocarbon solvent in a suitable apparatus for the production of extracts, at temperatures varying between about 10 C. and up to about 40 C., and for a period of time sufficient to extract at least about 5 per cent by weight of the thiophene tar. There appears to be nothing critical about the relative amounts of thiophene tar and of hydrocarbon solvent to be employed.

The preferred solvents are Cs-Ca.

Ordinarily, a proportion of at least about 1:1

and up to 4:1, by volume, of solvent to thiophene tar is used in one or more stages (up to four stages). The extract thus obtained is then subjected to a distillation to strip out the solvent.

. For example, thiophene tar is partially soluble in such hydrocarbons as normal heptane and isooctane (2,2,4-trimethyl-pentane). Accordingly, the thiophene tar is contacted with two parts by volume of normal heptane or isooctane at a temperature of 25 C. for about 40 minutes, and the liquid extract phase removed and subjected to distillation to remove the normal heptane or isooctane. The resultant product is wholly soluble in fuels of boiling ranges suitable for the usual jet combustion devices.

The jet combustion fuels of the present invention may contain other materials or additives for improving other characteristics thereof. Gum inhibitors and starting aids are mentioned by way of non-limiting examples of other additives which may be present in the jet combustion fuels of the present invention.

The addition of thiophene tar and of its extracts may be made to fuels of a fairly wide variety of boiling ranges, specific gravity, etc. Suitable base fuels for use in accordance with this invention include those having the character of-light gasolines up to those having the charactor of gas oils: Synthetic fuels, such as those manufactured by the Fischer-Tropsch process, can be used, as can be fuels derived from coal or wood distillation. It is also contemplated to add these combustion improving additives to liquid alcohols or combinations of alcohols with other base fuels. The preferred fuel is, however, a hydrocarbon distillate fuel boiling within the range of about F. to about 600 F.

The physical characteristics of typical suitable base fuels are given hereinafter for illustrative purposes:

1. Hydrocarbon distillate fuel:

Boiling range -535 F.

Gravity 53 A. P. I.

Vapor pressure 5.4 Reid, pounds.-

Freezing point Below '76 F.

Sulfur 0.03%, by weight.

Bromine No 15.

Aromatics 15%, by volume.

Viscosity .773 centistokes,

at 100 F.

2. Reference fuel A:

Boiling range 205-225 F.

Gravity 71.6 A. P. I.

Vapor pressure 1.7 Reid, pounds.

Freezing point Below '76 F.

Sulfur Nil.

Bromine No 0.

Aromatics 0.

Viscosity .623 centistokes,

at 100 F. 3. Reference fuel B:

Boiling range 320-470 F.

Gravity 365 A. P. I.

Freezing point Below -76 F.

Sulfur 0.035%, by weight.

Bromine N0 1,

Aromatics 12.1%, by volume.

Viscosity 1.48 centistokes,

at 100 F.

The following examples are given for the purpose of illustrating the present invention and for indicating the advantages thereof. It must be clearly understood, however, that these exam- 'aeiaorc pies are non-limiting. It will be appreciated by those skilled in the art that numerous types of jet combustion fuels, other than the reference fuels described hereinbefore, may be used for the purpose contemplated herein.

Thiophene tar in a concentration of about 0.5 per cent by weight in reference fuel B was sub- .jected to comparison test runs against the same fuel in a General Electric I-16 combustion chamber. Fuel flow and air flow were adjusted to simulate combustion conditions under actual operation in jet propelled aircraft equipped with a General Electric I-16 burner. Deposit formation was quantitatively evaluated by weighing the liners of the combustionichamber before and after burning a specified amount of fuel. The results of this test are shown in Table I.

Table I Reduction Deposit Fuel Weight 111 Deposits Percent phene Tar 4. 9

As another example illustrative of this invention, the rate of flame propagation using reference fuel A (substantially 2,2,4-trimethylpentane) was compared with that of a blend of the reference fuel A with 0.5 per cent by weight of the n-heptane extract of thiophene tar, in accordance with the procedure of Smith and Pickering hereinbefore disclosed. The fuel mixture was maintained at a temperature of about 230 F., under a pressure of 1 atmosphere, and the air flow rate was controlled at 3.15 pounds/hour. A similar test was conducted using a blend of 99.5 per cent of reference fuel A with 0.5 per cent of the isooctane extract of thiophene tar, previously disclosed. The results of these tests are shown in Table II.

It will be seen that by adding as little as 0.5 per cent of the extract material obtained from thiophene tar to the fuel, a substantial increase in rate of flame propagation is obtained, which, as indicated hereinbefore, means a substantial improvement in combustion stability.

This application is a continuation-in-part of copending application, Serial No. 744,023, filed April 25, 1947, now abandoned.

What is claimed is: I

l. A liquid fuel capable of being utilized in jet-combustion mechanisms, which comprises a hydrocarbon distillate having an initial boiling point of about 40 C. and a final boiling point of about 315 C. and boiling substantially continuously between said points, and between about 0.1 per cent byweight and about 2.0 per cent by weight of thiophene tar obtained by the process which includes separately preheating sulfur and a C4-hydr0carbon selected from the group consisting of normal butane, normal butenes and butadienes, to temperature such that combining said sulfur and said C4-hydrocarbon will give a reaction mixture having a temperature falling within the range varying between about 450 C. and about 760 (3.; mixing the preheated sulfur and the preheated Ci-hydrocarbon; reacting said preheated sulfur with said preheated C r-hydrocarbon at a reaction temperature falling within the range varying between about 450 C. and about 760 C. for a period of time selected to minimize the yields of hydrocarbons containing less than four carbon atoms per mol ecule and carbon disulfide at said reaction temperature, to yield a mixture containing thiophene tar; immediately reducing the temperature of the mixture containing said thiophene tar to a temperature of less than about 450 C.; and separating the thiophene tar from said mixture.

2. A liquid fuel capable of being utilized in jetcombustion mechanisms, which comprises a hydrocarbon distillate having an initial boiling point of about 40 C. and a final boiling point of about 315 C. and boiling substantially continuously between said points, and between about 0.1 per cent by weight and about 10.0 per cent by weight of thiophene tar obtained by the process which includes separately preheating sulfur a C4-hydrocarbon selected from the group consisting of normal butane, normal butenes and butadienes, to temperatures such that combining said sulfur and said C r-hydrocarbon will give a reaction mixture having a temperature falling within the range varying between about 450 C. and about 760 C.;

mixing the preheated sulfur and the preheated Ci-hydrocarbcn; reacting said preheated sulfur with said preheated Ci-hydrocarbon at a reaction temperature falling within the range varying between about 450 C. and about 760 C. for a period of time selected to minimize the yields of hydrocarbons containing less than four carbon atoms per molecule and carbon disulfide at said reaction temperature, to yield a mixture containing thiophene tar; immediately reducing the temperature of the mixture containing said thiophene tar to a temperature of less than about 450 C.; and separating the thiophene tar from said mixture.

3. A liquid fuel capable of being utilized in jetcombustion mechanisms, which comprises a hydrocarbon distillate having an initial boiling point of about 40 C. and a final boiling point of about 315 C. and boiling substantially continuously between said points, and between about 0.1 per cent by weight and about 2.0 per cent by weight of an extract of thiophene tar obtained by the process which includes separately preheating sulfur a C r-hydrocarbon selected from the group consisting of normal butane, normal butenes and butadienes, to temperatures such that combining said sulfur and said C r-hydrocarbon will give a reaction mixture having a temperature falling within the range varying between about 450 C. and about 760 C.; mixing the preheated sulfur and the preheated C r-hydrocarbon; reacting said preheated sulfur with said preheated C r-hydrocarbon at a reaction temperature falling within the range varying between about 450 C. and

about 760 C. for a period of time selected to minimize the yields of hydrocarbons containing less than four carbon atoms per molecule and carbon disulfide at said reaction temperature, to yield a mixture containing thiophene tar; immediately reducing the temperature of the mixture containing said thiophene tar to a temperature of less than about 450 (3.; separating the 9 thiophene tar from said mixture; treating said thiophene tar with a C5C8 alkane hydrocarbon solvent, to produce a hydrocarbon extract; separating the hydrocarbon extract; and removing the hydrocarbon from the hydrocarbon extract, to obtain the extract.

4. A liquid fuel capable of being utilized in jetcombustion mechanisms, which comprises a hydrocarbon distillate having an initial boiling point of about 40 C. and a final boiling point of about 315 C. and boiling substantially continuously between said points, and between about 0.1 per cent by weight and about 10.0 per cent by weight of an extract of thiophene tar obtained by the process which includes separately preheating sulfur a C r-hydrocarbon selected from the group consisting of normal butane, normal butenes and butadienes, to temperatures such that combining said sulfur and said C4-hydrocarbon will give a reac.---

heated C4-hYd1OC5L1bGI1; reacting said preheatedsulfur with said preheated C r-hydrocarbon at a reaction temperature falling within the range varying between about 450 C. and about 760 C. for a period of time selected to minimize the yields of hydrocarbons containing less than four carbon atoms per molecule and carbon disulfide at said reaction temperature, to yield a mixture containing thiophene tar; immediately reducing the temperature of the mixture containing said thiophene tar to a temperature of less than about 450 C.; separating the thiophene tar from said mixture; treating said thiophene tar with a C5C8 alkane hydrocarbon solvent, to produce a hydrocarbon extract; separating the hydrocarbon extract; and removing the hydrocarbon from the hydrocarbon extract, to obtain the extract.

5. A liquid fuel capable of being utilized in jetcombustion mechanisms, which comprises a hydrocarbon distillate having an initial boiling point of about 40 C. and a final boiling point of about 315 C. and boiling substantially continuously between said points, and between about 0.1 per cent by weight and about 2.0 per cent by weight of an extract of thiophene tar obtained by the process which includes separately preheating sulfur a Cir-hydrocarbon selected from the group consisting of normal butane, normal butenes and butadienes, to temperatures such that combining said sulfur and said Ci-hydrocarbon will give a reaction mixture having a temperature falling within the range varying between about 450 C. and about 760 C.; mixing the preheated sulfur and the preheated C4-hYdI'OC3IbOD; reacting said preheated sulfur with said preheated C r-hydrocarbon at a reaction temperature falling within the range varying between about 450 C. and about 760 C. for a period of time selected to minimize the yields of hydrocarbons containing less than four carbon atoms per molecule and carbon disulfide at said reaction temperature, to yield a mixture containing thiophene tar; immediately reducing the temperature of the mixture containing said thiophene tar to a temperature of less than about 450 C.; separating the thiophene tar from said mixture; treating said thiophene tar with a C3-Cl0 alkane hydrocarbon solvent, to produce a hydrocarbon extract; separating the hydrocarbon extract; and removing the hydrocarbon from the hydrocarbon extract, to obtain the extract.

6. A liquid fuel capable of being utilized in jet-combustion mechanisms, which comprises a hydrocarbon distillate having an initial boiling rately preheating sulfur a Ci-hydrocarbon selected from the group consisting of normal butane, normal butenes, and butadienes, to temperaturessuch that combining said sulfur and said C4-hydrocarbon will give a reaction mixture having a temperature fallin within the range varying between about 450 C. and about 760 C.; mixing the preheated sulfur and the preheated Ci-hydrocarbon; reacting said pre heated sulfur with said preheated C r-hydrocarbon at areaction temperature falling within the range varying between about 450 C..and about 760 C. for a period of time selected to minimize the yields of hydrocarbons containing less than four carbonatomsgper molecule and carbon disulfide at said reaction temperature, to yield a mixture containingthiophene tar; immediately reducing the temperature of the mixture containing said thiophene tar to a temperature of less than about 450 C.; separating the chicphene tar from said mixture; treating said thiophene tar with a C3-C10 alkane hydrocarbon solvent, to produce a hydrocarbon extract; separating the hydrocarbon extract; and removing the hydrocarbon from the hydrocarbon extract, toobtain the extract.

t7. A liquid fuel capable of being utilized in jet-combustion:mechanisms, which comprises a hydrocarbon distillate having an initial boiling point of about 40 C. and a final boiling point of about 315 C. and boiling substantially continuously between said points, and between about 0.1 per cent by weight and about 2.0 per cent by weight of an extract of thiophene tar obtained by the process which includes separately preheating sulfur a C r-hydrocarbon selected from the group consisting of normal butane, normal butenes and butadienes, to temperatures such that combining said sulfur and said Ci-hydrocarbon will give a reaction mixture having a temperature falling within the range varying between about 450 C. and about 760 C.; mixing the preheated sulfur and the preheated C4- hydrocarbon; reacting said preheated sulfur with said preheated C ;-hydrocarbon at a reaction temperature falling within the range varying between about 450 C. and about 760 C. for a period of time selected to minimize the yields of hydrocarbons containing less than four carbon atoms per molecule and carbon disulfide at said reaction temperature, to yield a mixture containing thiophene tar; immediately reducing the temperature of the mixture containing said thiophene tar to a temperature of less than about 450 C.; separating the thiophene tar from said mixture; treating said thiophene tar with normal heptane, to produce a hydrocarbon extract; separatin the hydrocarbon extract; and removing the normal heptane from the hydrocarbon extract, to obtain the extract.

8. A liquid fuel capable of being utilized in jet-combustion mechanisms, which comprises a hydrocarbon distillate having an initial boiling point of about 40 C. and a final boiling point of about 315 C. and boiling substantially continuously between said points, and between about 0.1 per cent by weight and about 2.0 per cent by weight of an extract of thiophene tar obtained by the process which includes separately pre- 11 heating sulfur a C4hydrocarbon selected from the group consisting of normal butane, normal butenes and butadienes, to temperatures such that combining said sulfur and said C r-hydrocarbon will give a reaction mixture having a temperature fallin within the range varying between about 450 C. and about 760 C.; mixing the preheated sulfur and the preheated C4- hydrocarbon; reacting said preheated sulfur with said preheated Ci-hydrocarbon at a reaction temperature falling within the range varying between about 450 C. and about 760 C. for a period of time selected to minimize the yields of hydrocarbons containing less than four carbon atoms per molecule and carbon disulflde at said reaction temperature, to yield a mixture containing thiophene tar; immediately reducing the temperature of the mixture containing said thiophene tar to a temperature of less than about 450 C.; separating the tar from said mixture; treating said thiophene tar with isooctane, to produce a hydrocarbon extract; separating the hydrocarbon extract; and removing the isooctane from the hydrocarbon extract, to obtain the extract.

9. A liquid fuel capable of being utilized in jet-combustion mechanisms, which comprises a hydrocarbon distillate having an initial boiling point of about 40 C. and a final boiling point of about 315 C. and boiling substantially continuously between said points, and a minor proportion, suflicient to improve the combustion properties thereof, of a material selected from the groups consisting of (1) thiophene tar obtained by the process which includes separately pre- 12 heating sulfur a C r-hydrocarbon selected from the group consisting of normal butane, normal butenes and butadienes, to temperatures such that combining said sulfur and said C4-hydrocarbon will give a reaction mixture having a temperature falling within the range varying between about 450" C. and about 760 C.; mixin the preheated sulfur and the preheated C4- hydrocarbon; reactin said preheated sulfur with said preheated C r-hydrocarbon at a reaction temperature falling within the range varying between about 450 C. and about 760 C. for a period of time selected to minimize the yields of hydrocarbons containing less than four carbon atoms per molecule and carbon disulfide at said reaction temperature, to yield a mixture containing thiophene tar; immediately reducing the temperature of the mixture containing said thicphene tar to a temperature of less than about 450 C.; and separating the thiophene tar from said mixture; and (2) an extract of said thiophene tar obtained by treating said thiophene tar with a (Ia-C10 alkane hydrocarbon solvent, to produce a hydrocarbon extract; separating the hydrocarbon extract; and removing the hydrocarbon from the hydrocarbon extract, to ootain the extract.

JACK M. GODSEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,450,659 Hansford Oct. 5, 1948 2,515,927 Lukasiewicz July 18, 1950 

1. A LIQUID FUEL CAPABLE OF BEING UTILIZED IN JET-COMBUSTION MECHANISMS, WHICH COMPRISES A HYDROCARBON DISTILLATE HAVING AN INITIAL BOILING POINT OF ABOUT 40* C. AND A FINAL BOILING POINT OF ABOUT 315* C. AND BOILING SUBSTANTIALLY CONTINUOUSLY BETWEEN SAID POINTS, AND BETWEEN ABOUT 0.1 PER CENT BY WEIGHT AND ABOUT 2.0 PER CENT BY WEIGHT OF THIOPHENE TAR OBTAINED BY THE PROCESS WHICH INCLUDES SEPARATELY PREHEATING SULFUR AND A C4-HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF NORMAL BUTANE, NORMAL BUTENES AND BUTADIENES, TO TEMPERATURE SUCH THAT COMBINING SAID SULFUR AND SAID C4-HYDROCARBON WILL GIVE A REACTION MIXTURE HAVING A TEMPERATURE FALLING WITHIN THE RANGE VARYING BETWEEN ABOUT 450* C. AND ABOUT 760* C.; MIXING THE PREHEATED SULFUR AND THE PREHEATED C4-HYDROCARBON; RESULFUR AND THE PREHEATED C4-HYDROCARBON; REC4-HYDROCARBON AT A REACTION TEMPERATURE FALLING WITHIN THE RANGE VARYING BETWEEN ABOUT 450* C. AND ABOUT 760* C. FOR A PERIOD OF TIME SELECTED TO MINIMIZE THE YIELDS OF HYDROCARBONS CONTAINING LESS THAN FOUR CARBON ATOMS PER MOLECULE AND CARBON DISULFIDE AT SAID REACTION TEMPERATURE, TO YIELD A MIXTURE CONTAINING THIOPHENE TAR; IMMEDIATELY REDUCING THE TEMPERATURE OF THE MIXTURE CONTAINING SAID THIOPHENE TAR TO A TEMPERATURE OF LESS THAN ABOUT 450* C.; AND SEPARATING THE THIOPHENE TAR FROM SAID MIXTURE. 